Not Your Mama's Sensor

More
rugged, adaptable and reliable sensors are being deployed in industrial
automation. The fact they’re taken for granted attests to how well they
perform.

Hollow
replicas of a bottle or other container are created to emulate the actual
package and house wireless sensors that measure impact, temperature and other
variables of production. Source: Sensor Wireless Inc.

When
the Lexus LS 460 debuted, its self-parking system created much of the initial
buzz. Formally known as the Advanced Parking Guidance System, the sensor-driven
device automatically eases into parallel-parking spaces.

Of course, it didn’t take long for the automotive crowd to laud the programming
and discount the sensors as the same technology that’s been around for decades.
After all, sensors are the Rodney Dangerfield of the automation world:
electronic systems don’t work without them, but they still get no respect. If
proximity and photoelectric sensors are so important, critics sniff, why
doesn’t anyone notice them?

In fact, being taken for granted may be the greatest complement for today’s
technology. Like other electronics, sensors are more robust, easier to use and
less expensive than ever before, and food companies and other manufacturers are
taking advantage of those improvements to develop new applications that reduce
waste and improve processes. Faster, smaller, lighter and cheaper is the mantra
of sensor fabricators, observes Jim Pankiewicz, sensor marketing manager at
Schaumburg, IL-based Omron Electronics LLC, and advancements in all four areas
are opening up new possibilities in inspection and quality assurance throughout
the supply chain.

Sensor technologies that may have been reserved for medical and other advanced
applications are finding their way onto the plant floor. Ultrasonic sensors are
a case in point. Flat beer was the top complaint at one major brewery, recalls
Carl Bonnan, general manager at Heuft USA Inc., the Downers
Grove,
IL, division of a German firm specializing in automated quality-assurance
technology. Internal pressure is a reliable indicator of lost carbonation, but
non-destructive measurement posed a challenge. Engineers used an ultrasonic
sensor to measure the magnetic field above the crown, using amplitude,
frequency and another undisclosed parameter above the crown to extrapolate
pressure. “That sensor has pretty much eliminated flat beer as a consumer complaint,”
maintains Bonnan.

The logarithm that calculates pressure based on the sensor’s inputs may be the
genius of the system, but the sensor is the enabling technology. “Years ago, manufacturers just did compliance
inspection,” Bonnan observes. “Now people want to know how good or bad the
product is so they can zero in on an issue before it becomes a problem.” The
savings from reduced waste are enormous, and sensors invariably underlie the
solution.

Industry
is demanding rugged photoelectric sensors that can stand up to caustic
chemicals and high-pressure washdowns, and sensor makers are trying to respond
with IP69K compliant units. Source: Omron Electronics LLC.

Sensors
are stand-ins for human senses, and no where is this more apparent than with
photoelectric devices. A low cost option to complex vision systems,
photoelectric sensors are penetrating new areas of the plant and expanding the
ability to manage processes. One consequence is the introduction of beefier,
detergent- and moisture-resistant sensors. Omron introduced a 316 stainless
steel housing for its E3ZM photoelectric sensor last year, an upgrade driven
“almost exclusively by food & beverage because of the stringent cleaning regiment,”
says Pankiewicz. “We try to mimic what our eye tells us with these sensors: is
it color, distance, or orientation we’re trying to sense?” Photoelectric
devices can handle all these tasks, but they also must withstand rapid
temperature cycling and other industrial abuses.

Like Omron, Rockwell Automation is seeking IP69K certification for heavy-duty
sensors, according to J.J. Thiara, marketing manager-photoelectric sensors. “It
started out with proximity/ inductive sensors and is expanding to other units,”
he says.

Photoelectric sensing range has gradually increased, “but a lot of times it
isn’t the range but the precision that a customer wants,” Thiara says. As
background color and contrast changes, sensors can be fooled; unlike the human
eye, they can’t adjust to changing conditions. Nonetheless, flexible
manufacturing demands adaptability, Thiara notes, and simplified teach
functions are being engineered into some sensors to adapt the focal plain as
needed.

A teach function that can be executed by a low-skill operator or remotely is a
growing demand, Pankiewicz agrees. On-board ASIC (application specific
integrated circuits) components are compact and affordable enough for inclusion
in “mildly complex sensors,” he says. These microprocessors also can store
multiple settings to adapt to line changeovers.

Multi-function sensors are another notable development. Instead of requiring
two or more inputs to a PLC, these units can perform logic, timing, counting
and other functions with a single device. “By reducing the I/Os on the PLC, you
also reduce the lines of code that have to be written,” Pankiewicz points out.

Look, ma, no wires

Wireless
sensing is the new frontier in industrial sensing, with reliability the caveat
most often raised. Some believe reliability no longer is an impediment: power
source is the bigger hurdle, particularly for active devices.

Nine years ago, Canada’s Sensor Wireless Inc., Charlottetown, PEI, introduced
SmartSpud, the first in a series of wireless sensors that measure impact on a
vegetable or packaged food product during processing. Those early devices
relied on a C battery to transmit data to a device 20 ft. away, recalls Tom McDonald,
senior product development technologist. Today, a cell similar to a digital
camera’s battery powers the sensor and transmits results to a personal digital
assistant up to 50 ft. away.

Four years ago, the firm’s technicians created their first sensor for
monitoring impact levels on a bottling line. An exact replica of a client’s
bottle was created and hollowed out, with sensors placed at the shoulder, heel
and other impact points. Instead of storing data for later download, as a data
logger would do, the device used radio frequency to provide real-time readings
as the mock bottle made its way down the line. “By capturing acceleration
impact at five points, bottlers can make preemptive changes to a line each time
they lubricate or make some other change, instead of reacting to maintenance
issues,” McDonald says.

Use of the ersatz bottles is taking off in the UK, thanks to a lightweighting
campaign funded by the government and encouraged by major retailers, notably
Tesco. The goal is to slash 65,000 tons of glass and 48,000 tons of related
carbon emissions from the supply chain within two years by reducing the
thickness of glass containers. Glass manufacturers specify the impact standard
of their lightweighted bottles, Sensor Wireless technicians correlate the
standard to G-force, and the mock bottles record what actually transpires when
the bottles roll down a line.

Within 50 ft. of the replica bottle, 99.6%-99.7% of transmitted data is
captured, says McDonald. “Nobody can guarantee 100% of the data, and that’s why
there’s a lag in getting QA to convert from pen-and-paper data logging.” For
process control, the gap is negligible and easily corrected by simply running
the replica through the line again.

The next goal for Sensor Wireless is to incorporate GPS with their replica
containers to relay data as product moves through the distribution system. They
will be following in the path of firms such as Novazone Inc., a Livermore, CA, provider of ozone-based
applications for food companies. Novazone recently launched PurFresh, a
sensor-based system that adds measured amounts of ozone to a refrigerated truck
or shipping container to slow ripening and kill mold and bacteria during
produce transport. Sensors measure temperature, humidity, ozone levels and
other factors and relay the data via LAN to a control unit built into the cover
of the refrigeration unit, according to Michael Weber, Novazone’s vice
president-engineering.

“Reliability of the sensor network was a concern; there are lots of home
networks available, but in an industrial environment, even cell phone reception
or BlueTooth can be spotty,” says Weber. Novazone selected a time synchronized
mesh protocol from Dust Networks to provide redundant data networking (see
sidebar on page 87). “In a refrigerated container, power is not an issue,”
Weber adds, making reliability the top design consideration.

Sensors
embedded in the cover of a refrigeration unit regulate the dispersion of ozone
to minimize produce spoilage during trucking and oceanic shipping. Source:
Novazone Inc.

Nanoscale sensing

Biosensors
have had an up and down relationship in food, mostly down. A recent example is
Advanced Biosensors Inc., a Hunt Valley, MD, venture that introduced engineered
biosensors that emitted light from a calcium sensitive, bioluminescent molecule
when a specific pathogen attached itself to the biosensor (“A better
germ-detecting mousetrap,” Food Engineering, May 2005). B-lympocytes to detect
E. coli, Lysteria and other organisms were developed to deliver reliable
results and few false positives in a matter of hours, not days as with
conventional biodetection cultures.

Advanced Biosensors targeted the food industry when its biosensor technology
was rolling out commercially two years ago, but recently the company has
shifted to anthrax detection and other biohazards. “There doesn’t seem to be
much impetus to do wholesale food testing,” says Rick Thomas, vice
president-business development. Advanced Biosensors recently “made the
strategic decision to move away from the food area and move toward defense and
biotech,” he says.

An amino assay of a different sort has been under development for almost 20
years at the Georgia Tech Research Institute (GTRI). Its developers remain
firmly committed to the food industry, in particular the poultry segment.
GTRI’s biosensors employ optical waveguide interferometers to detect the
presence of viruses and pathogens. Rapid detection with a low-cost test always
were twin objectives, and a year and a half ago, researchers upped the ante and
began developing an in-line system, according to David S. Gottfried, the senior
research scientist heading the project. That would transform the biosensor from
a lab-based instrument to an operations control tool, he says.

Sensors
are the enabling technology in Heuft’s inspection system that measures internal
bottle pressure with frequency and amplitude inputs to a logarithmic formula.
An ultrasonic sensor (inset) is used in the application. Source: Heuft USA Inc.

A
reusable optical chip needs to be developed to make the biosensor commercially
practical. The rest of the electronic hardware is readily available for less
than $1,000, and detection levels below 500 cells per milliliter have been
demonstrated. Field tests for Avian Influenza (AI) detection and chill-water
quality may be done this summer. AI testing with deliberately infected chickens
would have to be conducted in a Level 3 biohazard chamber, and that is
problematic. Pathogen detection in chiller water “is probably easier to field
test,” Gottfried acknowledges, bringing that application of the technology
closer to reality.

Processors typically sample chiller water weekly because testing is costly,
labor intensive and time consuming, he says. By providing an inexpensive way to
monitor bacteria levels and giving plant operators a clearer idea of what is
going on in the chillers, researchers hope to enhance chiller management
systems that use less water, minimize the likelihood of foodborne outbreaks and
reduce the cost of excessive use of disinfectants.

“I’m a chemist, and while we’ve resolved some of the chemistry issues, there
are a number of engineering issues that still need to be resolved,” admits
Gottfried. “The research is still somewhat in its infancy.” Still, development
of a working model is progressing, and refinements and optimization will
continue long after the first commercial biosensors become available.

The same kind of continuous improvement applies to wireless, photoelectric and
other types of sensors. The culmination of little improvements add up to
significant advances. Lexus’ APGS seems like whiz-bang technology now, but it
requires the driver to first align a yellow flag on a screen with a box
representing a parking space at least 78 inches longer than the car before
easing up on the brake and letting APGS go through its paces. The day when
drivers can simply exit and car and bark, “Park!” arrives, people will applaud
the on-board computer and say, “The sensors are the same as they were in 2007.”

ROI on wireless sensor networks spotlighted

Reliability
and power consumption are two of the biggest stumbling blocks for wireless
sensor networks. Not only have those issues been resolved, insists Rob Conant,
co-founder of Hayward, CA-based Dust Networks, but low-cost solutions are
beginning to be deployed in food operations.

“Reliability had been an issue for a long time, and it’s a deeply held belief
that it remains to be an issue with wireless,” observes Conant. “With time
synchronized mesh protocol, even if one link for data transmission is blocked,
wireless networks have four or five other paths through which information can
be routed.”

Sensors and actuators for valves and other devices remain tied to a local power
source, but sensors for communications networks have solved the power riddle.
Mesh networking technology “exceeds 99.9% reliability, even in metal canyons,”
he says. “Our engineers’ relentless focus on low energy demand has allowed us
to develop products that can go years without changing batteries.” Wireless
slashes installation costs and eliminates the “huge rat’s nest of wires if
you’re deploying thousands of vibration sensors,” he adds.

Petrochemical companies are converting to wireless networks en mass, and food
companies soon will follow: Cargill was sufficiently impressed with mesh
networks to take an equity position in Dust Networks. “They see a ton of opportunities for wireless
to improve their operations,” says Conant.

Did you enjoy this article? Click here to subscribe to Food Engineering Magazine.